The Chicago Clinical Treatment Unit (CTU) plans to participate in the clinical research proposed by the International Maternal Pediatric Adolescent AIDS Clinical Trial (IMPAACT) network. Our goal is to participate in protocols that are hypothesis-based and pathogenesis-oriented trials designed to 1) advance the ability to interrupt mother-to-child transmission of HIV; 2) improve prevention and treatment interventions for children and adolescents in the United State and internationally; 3) evaluate treatments and prevention of co-infections and co-morbidities in HIV-infected children, adolescents and pregnant women; 4) evaluate vaccines for the prevention of HIV, or to boost the immune system of HIV-infected children and adolescents. The proposed four units of the Chicago CTU are located in different parts of the world. In Chicago, the wide-range catchment area of the Chicago Clinical Research Sites (CRS) and the linkages they have developed with many community-based agencies will allow us to reach effectively many of the children, adolescents and women known to be affected by the HIV epidemic in Chicago and the surrounding area. The addition of the two international CRSs will strengthen the ability of the CTU to pursue (and hopefully answer) scientific questions which are important to the international community where the majority of the pediatric and adolescent patients are located. US-based researchers with 20-plus years of HIV/AIDS expertise will share their experience and help the international sites to be more effective in their efforts to enroll and follow the large numbers of HIV-infected children, adolescents and women in South Africa and Thailand. ADMINISTRATIVE COMPONENT